Transient Performance Analyze On Protective Current Transformers

In order to study the performance of protective current transformers under the transient situations occurred in power system. A serial models were created and simulated with Matlab/Simulink in this paper.Hysteresis shall been take into account to identify the performance of current transformers. Based on the Preisach Model, a new “Markov Effect” hysteresis model was built. And based on this, a model of current transformers which with hysteresis was took into simulation.And then, with the module mentioned above, simulations were taken to study the transient performance of protective current transformers widely separated in China power system, especially the performances of saturated current transformers caused by different load conditions. The conclusions were descript as following.Respect to normal protective current transformers, the waveforms of saturated secondary current will be obviously different relate to the load characteristics. In brief, the inductive portion of the secondary load is the main part that will influences the transient performance of current transformers.But, for the TPY class current transformers on purpose of transient protection that was widely used in UHV and EHV power system, the main cause that influence the transient performance is the resistance part of the secondary load. To a certain current transformer, the lower the resistive component of the secondary load, the harder the transformer be saturated. In another word, the better the transient performance is.